Corrosion protecting compositions



Patented Aug. 26, 1947 UNITED Francis F. Farley, Alton, Ill., assignor to Shell Development Company, San Francisco, Calif.,

a corporation of Delaware No Drawing. Application March 21, 1944, Serial No. 527,493

7 Claims. (oi. 252-395) This invention relates to new and useful rustproofing compositions. More particularly, it pertains to novel corrosion or rust retarding agents and especially to their employment in substantially neutral polar vehicles. The invention may be exemplified by rust-proofing slushing fluids or metal treating baths, by rust inhibiting antifreeze compositions, by aeronautical deicing fluids, and by aqueous solutions particularly adapted to treating metallic surfaces, which solutions contain the herein described corrosion inhibiting components.

Solutions or suspensions of Various dibasic acids, in particular relatively high molecular Weight dicarboxylic acids have been employed in oily media such as hydrocarbons or lubricating oil to impart rust protection to metallic surfaces. Various applications of such corrosion treating with an oily vehicle, however, have left room for considerable improvement, For example, semi-finished metal parts are often set aside for a period of time before additional machining or other treatment. During this waiting period it is often very essential that they be rigidily protected against rusting or corrosion which may be set in force even by handling or by the moisture in the atmosphere. However, if they are treated by a slushing oil to impart rust protection, the 7 remaining oily film may be objectionable during subsequent treatment or use of the metal. For example, if it is required to paint the metallic object, an oil free surface is desirable. Or if the finished metal is to come in contact with silk or other fabric, an oil-free surface is a rigid requirement.

Also, the problem of rusting is often at its worst in environments of water or other polar solvents such as in machinery cooling systems (e. g. automobile radiators). In such aqueous media, the employment of dispersions of oil-soluble rust inhibitors leaves much to be desired. Although such carboxylic rust preventives may be colloidally dispersed in aqueous or non-oily media, as in an anti-free composition, such a composition is obviously less stable (and hence less effective as a rust preventive) than would be a corresponding true solution. For example, oil soluble alkyl succinic acid of approximately 650 mol. wt. gives in ethylene glycol a turbid solution (or suspension) from which it tends to settle out gradually. Accordingly, it is an object of the invention to increase the corrosion resistance of metals, particularly of iron, and especially of those metals which come in contact with water or aqueous media, Another purpose is the production of rust inhibited metal articles or of metals having decreased corrosive tendencies, without the ,employment of oily treating compositions. Other objects are the production of improved slushing fluids, anti-freeze compositions, deicin fluids and metal treating compounds. Additional objects will be apparent from the present description and claims,

It has now been found that the alkali metal or ammonium acid salts of aliphatic dibasic acids which contain at least one free carboxyl radical or its thio equivalent possess excellent corrosion inhibiting properties. Such compounds should contain a minimum of about 12 carbon atoms, more preferably at least 16 or 20. The acid radiicals should be as close to each other as possible, that is, separated from each other by not more than four and preferably not more than three intervening atoms.

For example, the dibasic acids, the alkali metal or ammonium acid salts of which are employed according to the present invention, may be alkyl malonic or alkyl succinic acids as represented by the formulae I COOH it It The oxygen in the acid radical may also be replaced in whole or in part by sulfur to give thio equivalents such as thiolic COSH, thionic CSOH,,or thionothiolic -CSSH radicals.

One of the closely placed acid radicals need not be a carboxylic radical or corresponding thio radical but instead may be a mercapto, cyano, nitro, nitroso, etc., radical as in hydroxamic acids NOH alpha or beta cyano- R-CH-C on N nitro- R--CH-C 0 on I110:

nltroso- R-CHCO0H to or mercapto- (R-(|JHCOOH) etc., carboxylic acids.

For purposes of stability the compounds should be free of olefinic and acetylenic bonds, although they may contain preferably not more than one olefinic bond per molecule. The acids may also contain one or more polar substitution radicals which do not impair the stability of the acids toward oxidation or hydrolysis and which preferably are not more strongly acidic than the carboxylic radicals of the acids, such as halogen, alcoholic --OH,

etc.

The acid salts of the present invention are prepared by half neutralizing with an alkali metal or ammonia base the aliphatic dibasic acids exemplified above. By half neutralizing is meant the neutralization of only one of the two acidic groups per molecule, for instance with lithium, sodium, potassium or ammonium hydroxides. Thus, for example, one mol of an alkyl succinic acid would be reacted with one mol of potassium hydroxide to yield the mono potassium acid alkyl succinate.

It is important that the dibasic acid be only half neutralized. If both acidic groups are neutralized, as for example, di-potassium or di-sodium alkyl succinate, the neutral compound is inferior in rust inhibiting properties. In addition, some such neutral salts as iron alkyl succinate seem to be pro-oxidants which greatly diminishes the rust inhibiting effectiveness of unneutralized alkyl succinates with which they may be associated.

The present compounds may be advantageously employed in polar compounds such as aqueous media. Many of them are completely soluble in rust protective amounts in water itself. With others of lesser aqueous solubility, the presence of another polar compound, such as a monoor polyhydroxy alcohol, increases their solubility suillcient for adequate rust protection. However, employment of the present compounds in colloidal dispersion, as well as solution, in polar as well as non-polar media, is also contemplated.

The substantially neutral polar compounds may be weakly acidic or basic, preferably having a dissociation constant not above about 10-. Sub- 4 stances such as the following may be employed individually or together:

Water, alcohols, such as methyl, ethyl, propyl, isopropyl, butyl, amyl, hexyl, cyclohexyl, heptyl, methyl cyclohexyl, octyl, decyl, lauryl, myristyl, cetyl, stearyl, benzyl, etc. alcohols; polyhydric alcohols as ethylene glycol, propylene glycol, butylene glycol, glycerol, methyl glycerol, etc.; phenol and various alkyl phenols; ketones as acetone, methyl ethyl ketone, diethyl ketone, methyl Dropyl. methyl butyl, dipropyl ketones, cyclohexanone, and higher ketones; keto alcohols as benzoin; ethers as diethyl ether, di-isopropyl ether, d-ethylene di-oxide, beta beta di-chloro dichloro di-ethyl ether, di-phenyl oxide, chlorinated di-phenyl oxide. (ii-ethylene glycol, tri-ethylene glycol, ethylene glycol monomethyl ether, corresponding ethyl, propyl, butyl, etc., ethers; neutral esters of carboxylic and other acids as ethyl, proply, butyl, amyl, phenyl, cresyl and higher acetates, propionates, butyrates, lactates, laurates, myristates, palmitates, stearates, oleates, ricinoleates, phthalates, phosphates, phosphites, thiophosphates. carbonates; natural waxes as carnauba wax, candelilla wax, Japan wax, jojoba oil, sperm oil, fats as tallow, lard oil, olive oil, cottonseed oil, perilla oil, linseed oil, tung oil, soyabean oil, flaxseed oil, etc.; weak bases as pyridines, alkyl pyridines, quinolines, petroleum bases, etc.

Vehicles of little or no polarity with which the present compounds may be used comprise hydrocarbons or halogenated hydrocarbons as liquid butanes, pentanes, hexanes, heptanes, octanes, benzene, toluene, xylenes, cumene, tetraline, indene, hydrindene, alkyl naphthalenes; gasoline distillates, kerosene, gas oil, lubricating oils (which may be soap-thickened to form greases), petrolatum, paraflln wax, albino asphalt, carbon tetrachloride, ethylene dichloride, propyl chloride, butyl chloride, chlorbenzol, chlorinated kerosene, chlorinated parailin wax, etc.

A particular adaptation of the present invention is the employment in a medium (or media) comprising both polar and non polar substances, of both the half neutralized and unneutralized rust inhibitors. For example, gasoline is frequently stored over water consciously or inadvertently. This may result in considerable economic loss by rusting. Now, by the employment of both classes of rust inhibitors, the unneutralized acids will afford rust protection predominantly for the gasoline phase and the half neutralized salt predominantly for the aqueous phase. In this manner rusting may be very substantially eliminated. Similar inhibitor mixtures may likewise be employed in vehicles containing both polar and non polar components such as flushing oil, cutting oils, etc.

On the other hand, when the vehicle is composed chiefly of water soluble or polar compounds, for example an anti-freeze solution such as is used in an automotive radiator, it is advantageous to employ the half neutralized salts. Such an anti-freeze solution may contain substantial amounts of water-soluble, neutral organic liquids, such as lower alcohols, e. g. methyl, ethyl, n-propyl, isopropyl, tertiary butyl alcohols, ethylene glycol, propylene glycol, butylene glycols, glycerine; ethers, such as diethyl ether, dioxane; alcohol ethers as diethylene glycol, triethylene glycol, ethylene glycol mono methyl, ethyl or propyl ethers, diethylene glycol mono methyl, ethyl, or propyl ethers; ketones, as acetone, diacetone alcohols; nitriles as acetonitrile; etc.

A particular application for the present acid salts is in aviation de-icing fluids which are applied, for example, to the wings and propellers of airplanes. Such compositions normally comprise water and one or more water miscible organic hydroxy compounds like monoand polyhydroxy alcohols, such as ethyl-, di-acetone-, secondary butyl-, isopropyl-alcohol, ethylene glycol, glycerin, etc. to which mixture may be added a noninflammable, low freezing material such as carbon tetrachloride, di-fiuor di-chlor methane, chloroform, chloral, etc., as well as, if desired, oxidation inhibitors, corrosion inhibitors, etc. In such compositions the present acid salts act as corrosion inhibitors, as well as wetting and spreading agents which cause the deicing fluid to flow more evenly over the surface to be deiced and prevent adherance of moisture even after the flow of the deicing fluid has stopped, thereby retarding the building up of a layer of ice for considerable periods.

In rendering metallic surfaces corrosion resistant by application of the acid salts, it is of course desirable that the metal be free from rust to start with. However, in some instances the acids may assist in the removal of rust or other oxide films, thus tending to clean the metallic surface if present in sufficient concentration. For this purpose a mild abrasive such as bentonite, silica powder, pumice, etc., may be applied simultaneously.

Application of the corrosion inhibiting composition on the cleaned metal surface may be carried out by any convenient means, such as painting, spraying, dipping, etc. Excessive amounts of the composition, if any, are simply allowed to drain off and the wet metal surface is allowed to dry.

After being applied, all or part of the vehicle may be evaporated, or it may be more or less permanent. In other words, for use as a slushing fluid, both volatile carriers may be used, or substances which do not materially volatilize under normal atmospheric conditions.- As to chemical requnirements, the vehicle should be reasonably stable under ordinary conditions of storage and use and be inert to the active inhibitors.

The protective effect of the treatment is particularly pronounced towards ferrous metals, e. g. various kinds of steel and iron. However, other metals normally susceptible to corrosion as copper, lead, aluminum, various alloys, e. g. brasses, bearing metals, etc., may be benefited as well.

It is understood that the corrosion-protective compositions of this invention may contain other ingredients in addition to the vehicle and the acid salts. However, such additional ingredients must be chemically inert to the acid and the vehicle employed. Thus, strong oxidizing agents such as chlorine, peroxides, etc., must be avoided as they tend to destroy the inhibitors. Strong bases, particularly in ionizing vehicles, as in water, alcohols, etc., will neutralize the acids and thereby render them relatively ineffective. Likewise, strong acids may reduce their effectiveness. However, in non-ionizing solvents, i. e. in hydrocarbon compositions, chlorinated hydrocarbons, etc., the presence of relatively small quantities of primary, secondary and tertiary nitrogen bases and/or monocarboxylic acids will not normally interfere with the activity of the inhibitor and may accelerate its reaction with the metal surface. On the other hand, even in these vehicles very strong bases as various onium bases, or very strong acids as sulfonic acids, should not be used.

The amounts of the acid salts which must be incorporated in suitable vehicles to produce corrosion-protective compositions vary considerably with the type of vehicle used. As a general rule, the presence of resinous materials, particularly those of a colloidal nature, calls for relatively larger amounts of inhibitors. Resinous materials which interfere with the activity of the inhibitors comprises asphaltenes, petroleum resins, various other natural resins, as rosin, resins formed by polymerization of drying fatty oils, phenol-formaldehyde resins, glyptal type resins formed by esteriflcation of polyhydric alcohols with polycarboxylic acids, etc.

I the absence of such resinous materials, amounts required of the acidic inhibitors vary from about 0.02% up to about 0.1% although larger amounts, say 1% or more, may be used. However, where the acids are in colloidal dispersion, rather than in true solution, a concentration in excess of about 0.1% may result in relatively quick loss of part of the inhibitor by precipitation and settling. In the presence of resinous materials amounts between 0. to 5% or even higher are usually desirable to obtain full corrosion protection.

Some of the advantages of the invention may be seen from the following example:

Alkyl succinic acid of approximately 650 mol. wt. was reacted with the calculated amount of KOH necessary to half neutralize it. 0.025% of this reaction product was dissolved in a mixture of 33%% ethylene glycol in distilled Water. A polished steel strip was immersed in this mixture at 167 F. At the end of 24 hours this strip I minimum of about 12 carbon atoms, both of the unneutralized dibasic aliphatic dicarboxyllc acid having a minimum of about 16 carbon atoms, the two acidic groups being separated by not more than about two carbon atoms, said half neutralized dicarboxylic acid being selected from the group consisting of ammonium and alkali metal acid salts.

3. A composition consisting essentially of a neutral fluid vehicle and a minor but corrosioninhibiting amount each of a half-neutralized and an unneutralized alkyl succinic acid containing a minimum of about 16 carbon atoms, said half neutralized succinic acid consisting of the mono potassium acid salt of said acid.

4. A composition consisting essentially of a neutral polar fluid vehicle and a minor but corrosioninhibiting amount each of a half-neutralized and an unneutralized dibasic aliphatic dicarboxylic acid having a minimum of about 12 carbon atoms,

7 the two acidic groups being separated by not more than about four intervening atoms. said halt neutralized dicarboxylic acid being selected from the group consisting of ammonium and alkali metal acid salts.

5. A composition consisting essentially of a neutral aqueous solution and a minor but corrosioninhibiting amount each of a half-neutralized and an unneutralized aliphatic dibasic acid having a minimum of 12 carbon atoms, both of the acidic groups being selected from the group consisting of carboxylic radicals and their thio equivalents, the two acidic groups being separated by not more than four intervening atoms, said half neutralized dibasic acid being selected from the group consisting of ammonium and alkali metal acid salts.

6. A composition consisting essentially of a pen-- tral aqueous solution and a minor but corrosioninhibiting amount each of a half-neutralized and an unneutralized alkyl succinic acid containing a minimum of 16 carbon atoms, said half neutralized succinic acid being selected from the group consisting of ammonium and alkali metal acid salts.

FRANCIS F. PARLEY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,878,468 Covell Sept. 20, 1932 1,915,148 Berliner et al June 20, 1933 1,966,711 De Groote et al July 17, 1934 1,993,773 Clarkson Mar. 12, 1935 2,292,308 Watkins Aug. 4, 1943 2,324,577 Hofiner et al. July 20, 1943 2,324,770 Donlan July 20, 1943 2,334,158 von Fuchs Nov. 9, 1943 2,349,044 Jahn May 16, 1944 2,353,210 Williams July 11 1944 

